Roller blinds are very popular for industrial use. However, one of the drawbacks of a conventional industrial roller blind is that the blind, being of substantial size, is often very heavy to rewind from a lowered position.
In typical home style smaller roller blinds, a coil spring is used as an automatic rewind for the blind. A lock is provided to hold the coil spring in different tensioning positions. The spring tension is substantially greater than the weight of the blind so that as soon as the lock is released the coil spring pulls the blind upwardly. This type of spring actuated return is fickle in that if the lock should release prematurely, the blind virtually flies upwardly and can often unwind on its mounting shaft. This type of an arrangement is not suitable for a much heavier industrial blind.
A type of industrial blind control that is available through General Clutch Corporation is one which uses a spring clutch tightening as the blind is unwound and loosening as the blind is lifted. However, there is no spring assist in the lifting of the blind which is accomplished by hand through a chain drive. This arrangement suffers from the drawback noted above, i.e. the awkwardness of handling the weight of a large industrial blind.